Integrated Compression Screw Versus Unicortical Locking Screw for Fixing the Dorsal Critical Corner in Distal Radius Fractures: A Biomechanical Study.

Purpose: Although studies have demonstrated that locked screws with a length of 75% of the radius width are sufficient for the treatment of extra-articular fractures of the distal radius, the application of this principle to intra-articular fractures is less well-understood. This study aimed to evaluate the biomechanical properties of different types of volar plate fixation constructs for the treatment of distal radius fractures in the presence of a dorsal critical corner fragment.

Methods: A dorsal critical corner fracture was created in 18 synthetic distal radius models. The fragment was stabilized with one of three constructs: a posteroanterior integrated compression screw (group 1) or volar locking screws with a length of 90% or 75% of the volar/dorsal width of the radius (groups 2 and 3, respectively). For the biomechanical evaluation, a load was applied to the lunate facet. Fixation stiffness and loads to produce clinical and catastrophic failures were compared among the groups.

Results: The stiffness (N/mm) was 67.8 (SD, 14.7), 64.9 (SD, 8.63), and 65.8 (SD, 36.02) for groups 1, 2, and 3, respectively. The load required to generate a catastrophic displacement was 532.9 (SD, 142.32), 307.4 (SD, 101.51), and 230.8 N (SD, 77.68) for groups 1, 2, and 3, respectively. The load required to produce a 2-mm translation of the fixed fragment was 127.9 N (SD, 28.8) for group 1, 119.7 (SD, 11.78) for group 2, and 127.6 N (SD, 46.2) for group 3.

Conclusions: Significantly greater load is required for catastrophic failure after fixation of a dorsal critical corner fracture with an integrated compression screw; however, it provides similar stiffness and load to failure for 2 mm of translation.

Clinical relevance: For the treatment of intra-articular distal radius fractures with dorsal critical corner fragments, an integrated compression screw may be considered for rigid fixation of the fragment to support early return to daily activities.